Recently, organic light-emitting displays have been attracting attention as planar displays of the next generation. These organic light-emitting displays have excellent characteristics, e.g., capacity of emitting white light, wide viewing angle and high-speed response.
An organic electroluminescent element (hereinafter referred to as organic EL element) disclosed by JP-A-2003-272860 is known. FIG. 2 illustrates a conventional organic EL element. It comprises the board 1 which supports the lower electrode 2 and upper electrode 6, and light-emitting unit 7, charge-generating layer 4-1, light-emitting unit 8, charge-generating layer 4-2, light-emitting unit 9, charge-generating layer 4-3 which are placed between these electrodes 2 and 6. The light-emitting units 7, 8 and 9 are responsible for emitting red, green and blue light, respectively. The conventional organic EL element illustrated in FIG. 2 has a layered structure comprising the light-emitting units connected to each other in series via the charge-generating layer in-between. The light-emitting units 7, 8 and 9 emit red, green and blue light, respectively, when a voltage is applied to between the lower electrode 2 and upper electrode 6. These light colors overlap each other to produce white light. Luminance L of white light emitted by the organic EL element illustrated in FIG. 2 can be given by the formula L=LR+LG+LB, where LR, LG and LB are each luminance of red, green and blue light emitted by the light-emitting units 7, 8 and 9. Luminance L of white light emitted by the organic EL element illustrated in FIG. 2 can be also given by the formula L=IαR+IαG+IαB, where αR, αG and αB are each light-emitting efficiency (current efficiency) of the respective light-emitting units 7, 8 and 9, and I is current passing through each of the these light-emitting units. Luminance L of white color emitted by the organic EL element illustrated in FIG. 2 is proportional to light-emitting efficiency of each light-emitting unit. In other words, the R/G/B luminance ratio is equal to αR/αG/αB.    (Patent Document 1) JP-A-2003-272860